Towers, masts, poles or the like (hereinafter simply called ‘vertical structure(s)’) are well know in the prior art. Each single structure, due to the complexity of the loads being applied and due to other factors, is generally custom designed to the customer's specific requirements (e.g. the owner of the structure, such as an electric power distribution company). In the case of structures for supporting transmission lines of an electric power transmission system, in addition to the vertical structure itself, they also comprise braces, arms or similar members to which the overhead conductors are connected; as well as other accessories and components suitable for the desired purposes. A general overview of the related art may be found, for instance, in the book written by COOMBS, R. D., Pole and tower lines for electric power transmission, Merchant Books, 2006 (1st ed. 1916). General guidelines about the subject matter may be found, for instance, in MAGEE, William L., Design of steel transmission pole structures, ASCE/SEI 48-05, ASCE, 2006 and in American Society of Civil Engineers, Subcommittee on Guyed Transmission Structures, Design of guyed electrical transmission structures, ASCE, 1997, as well as in other standards worldwide. GUNGER, Y. R. et al published the article Novel design of transmission towels from bent metallic sections of non-traditional shapes, Power Technology and Engineering, March, 2003, vol. 37, no. 2, p. 120-122 and articles available at the internet site www.elsi.ru of the ‘ÉLSI’ Research Production Association, titled ‘Use of new constructions of supports [ . . . ]’ (GUNGER, Y. R. et ZEVIN A. A.) and ‘New constructions of supports from [ . . . ] 220 kV’ (GUNGER, Y. R.). Additional exemplary embodiments for supporting transmission lines and or other loads, which in some cases are not designed and capable for supporting particularly transmission lines, may be found also in BR PI9606177; BR PI0501862; CH478322; DE2838239A1; DE3640479A1; FR592085; FR622027; FR648313; FR927829; FR1116601; FR1224955; FR1525288; GB668408; JP10-046872A2; JP 09-317242A2; JP2001-355352A2; JP2003-027768A2; JP2003-120072A2; JP2004-143920A2; JP2004-245042A2; JP2006-219898A2; NL1017638C; RU2083785C1; RU2136830C1; RU2204671C2; RU2204672C2(WO03004802A1); RU2197587C1(WO03010402A1); RU2197586C1(WO03010403A1); RU2248434C1; RU2256758C; U.S. Pat. No. 466,012; U.S. Pat. No. 1,179,533; U.S. Pat. No. 1,034,760; U.S. Pat. No. 1,200,453; U.S. Pat. No. 1,616,931; U.S. Pat. No. 2,064,121; U.S. Pat. No. 2,116,368; U.S. Pat. No. 2,401,799; U.S. Pat. No. 2,410,246; U.S. Pat. No. 3,196,990; U.S. Pat. No. 3,343,315; U.S. Pat. No. 3,504,464; U.S. Pat. No. 3,571,991; U.S. Pat. No. 3,865,498; U.S. Pat. No. 3,935,689; U.S. Pat. No. 4,314,434; U.S. Pat. No. 531,901; U.S. Pat. No. 5,687,537; U.S. Pat. No. 5,880,404; U.S. Pat. No. 6,286,281; U.S. Pat. No. 6,343,445; U.S. Pat. No. 6,668,498; US20040211149A1; U.S. Pat. No. 7,059,095; U.S. Pat. No. 7,098,552; WO97/21258A1; WO01/36766A1; WO01/83984A1; WO02/103139A1; WO2006/116863A1.
It is common for the customer to make available a ‘load tree diagram’ for each vertical structure loading variation or, more commonly, for a set of vertical structures loading variations. Nevertheless, there are some different types or configurations of structures that can be grouped into families because of their similar general shape, for instance monopoles, lattice towers, delta towers, etc. The expressions ‘monopole(s)’, ‘pole(s)’, ‘mast(s)’ or ‘single column towers’ are can be used as synonymous. Many factors are analyzed when determining the advantages and disadvantages of each type of vertical structure family, for instance: manufacturing costs; loads; maintenance considerations; construction ease and infrastructure required for construction; allowable spans and number of structures within a given length; area beneath conductors; structure footprint and need for foundations; impact on right-of-way, vegetation, environment; radio interference, audible noise, and electro-magnetic field; etc.
The load trees diagrams conventionally use an orthogonal coordinate system for specifying the loads, which are classified as: transverse, longitudinal, or vertical loads. For instance, in the case of a structure for an electrical power transmission line, the loads involved are: (i) vertical loads, such as weight of conductors, down-pull caused by level differences between the structures and ice loads; (ii) transverse loads, such as those caused by wind and horizontal pull from deviation angle in the line; (iii) longitudinal loads, such as those caused by pretension of conductor on one side only and by an abnormal load in case of, for instance, a broken wire. Other loads and effects are also considered when designing the structure, such as torsional shear, loads related to the weight of the vertical structure, aeolian vibration, stresses, etc.
In the case of lower tensions, generally up to approximately 64 kV, it is very common to use concrete, wood or steel monopoles. For higher tensions, during the 1950s through the 1970s, self-supporting steel lattice towers, with a general trunkpyramidal shape, H-frame poles, delta towers and the like, were the most common vertical structures built in most countries for electric power transmission lines because at that time they were considered relatively strong, light and could be erected without the need for heavy equipment and major access roads. Nevertheless, this kind of structures takes too much time to design and build; as well as their base foundation requires a large footprint area. Nowadays, steel monopoles are being widely adopted. Such monopoles are usually hollow multi-sided tubes connected together, having a general tapered shape from its bottom to its top. The increased use is because they are considered more aesthetically acceptable, require a smaller footprint and, consequently, have less impact on the right-of-way, and they are easy to transport and assemble in the field.
New designs for structures have been proposed recently. In ‘FIG. 1’ of the article mentioned supra ‘New constructions of supports from [ . . . ] 220 kV’, GUNGER shows three kinds of structures which are in use: two self-supporting latticed towers that also require large bases and one guyed tower with a smaller base, in which the guys are attached to the arm members and apparently in the tower, below the larger diameter of the tower which is close to the top of the tower. Different shapes with narrow bases are proposed by GUNGER as alternatives to these three structures.